[JavaScript知识库]用微信小游戏实现龙舟大战-打粽子

用微信小游戏实现龙舟大战-打粽子

端午节来啦！各位c粉有没有吃粽子啊！

前言

端午节来啦！今天沉默带大家来做个关于端午节的小游戏，我的设计思路是用龙舟打粽子，类似于飞机大战，只不过我们的场景是在河中。源码在文章后获取哟！

提示：以下是本篇文章正文内容，下面案例可供参考

一、体验视频

下面是小游戏的开发效果视频：

二、开发流程

1.素材收集

龙舟大战，我们需要一张龙舟的图片和粽子的图片，这里我们还需要河面的背景图片。值得注意的是，龙舟打粽子还需要子弹的图片，为了体现端午节的元素，我们将子弹设定为粽子，当子弹接触到前方的粽子时，前方粽子爆炸特效也需要通过图片生成。具体图片素材如下图：

2.游戏逻辑实现

2.1 定义游戏开发基础类

• 相关的代码说明请看注解

import Sprite from './sprite'
import DataBus from '../databus'

const databus = new DataBus()

const __ = {
  timer: Symbol('timer'),
}

/**
 * 简易的帧动画类实现
 */
export default class Animation extends Sprite {
  constructor(imgSrc, width, height) {
    super(imgSrc, width, height)

    // 当前动画是否播放中
    this.isPlaying = false

    // 动画是否需要循环播放
    this.loop = false

    // 每一帧的时间间隔
    this.interval = 1000 / 60

    // 帧定时器
    this[__.timer] = null

    // 当前播放的帧
    this.index = -1

    // 总帧数
    this.count = 0

    // 帧图片集合
    this.imgList = []

    /**
     * 推入到全局动画池里面
     * 便于全局绘图的时候遍历和绘制当前动画帧
     */
    databus.animations.push(this)
  }

  /**
   * 初始化帧动画的所有帧
   * 为了简单，只支持一个帧动画
   */
  initFrames(imgList) {
    imgList.forEach((imgSrc) => {
      const img = new Image()
      img.src = imgSrc

      this.imgList.push(img)
    })

    this.count = imgList.length
  }

  // 将播放中的帧绘制到canvas上
  aniRender(ctx) {
    ctx.drawImage(
      this.imgList[this.index],
      this.x,
      this.y,
      this.width * 1.2,
      this.height * 1.2
    )
  }

  // 播放预定的帧动画
  playAnimation(index = 0, loop = false) {
    // 动画播放的时候精灵图不再展示，播放帧动画的具体帧
    this.visible = false

    this.isPlaying = true
    this.loop = loop

    this.index = index

    if (this.interval > 0 && this.count) {
      this[__.timer] = setInterval(
        this.frameLoop.bind(this),
        this.interval
      )
    }
  }

  // 停止帧动画播放
  stop() {
    this.isPlaying = false

    if (this[__.timer]) clearInterval(this[__.timer])
  }

  // 帧遍历
  frameLoop() {
    this.index++

    if (this.index > this.count - 1) {
      if (this.loop) {
        this.index = 0
      } else {
        this.index--
        this.stop()
      }
    }
  }
}

2.2 帧动画的简易实现

const __ = {
  poolDic: Symbol('poolDic')
}

/**
 * 简易的对象池实现
 * 用于对象的存贮和重复使用
 * 可以有效减少对象创建开销和避免频繁的垃圾回收
 * 提高游戏性能
 */
export default class Pool {
  constructor() {
    this[__.poolDic] = {}
  }

  /**
   * 根据对象标识符
   * 获取对应的对象池
   */
  getPoolBySign(name) {
    return this[__.poolDic][name] || (this[__.poolDic][name] = [])
  }

  /**
   * 根据传入的对象标识符，查询对象池
   * 对象池为空创建新的类，否则从对象池中取
   */
  getItemByClass(name, className) {
    const pool = this.getPoolBySign(name)

    const result = (pool.length
      ? pool.shift()
      : new className())

    return result
  }

  /**
   * 将对象回收到对象池
   * 方便后续继续使用
   */
  recover(name, instance) {
    this.getPoolBySign(name).push(instance)
  }
}

2.3 游戏基本元素精灵类

(粽子.子弹.击中特效)

/**
 * 游戏基础的精灵类
 */
export default class Sprite {
  constructor(imgSrc = '', width = 0, height = 0, x = 0, y = 0) {
    this.img = new Image()
    this.img.src = imgSrc

    this.width = width
    this.height = height

    this.x = x
    this.y = y

    this.visible = true
  }

  /**
   * 将精灵图绘制在canvas上
   */
  drawToCanvas(ctx) {
    if (!this.visible) return

    ctx.drawImage(
      this.img,
      this.x,
      this.y,
      this.width,
      this.height
    )
  }

  /**
   * 简单的碰撞检测定义：
   * 另一个精灵的中心点处于本精灵所在的矩形内即可
   * @param{Sprite} sp: Sptite的实例
   */
  isCollideWith(sp) {
    const spX = sp.x + sp.width / 2
    const spY = sp.y + sp.height / 2

    if (!this.visible || !sp.visible) return false

    return !!(spX >= this.x
              && spX <= this.x + this.width
              && spY >= this.y
              && spY <= this.y + this.height)
  }
}

2.4 粽子类实现过程

import Animation from '../base/animation'
import DataBus from '../databus'

const ENEMY_IMG_SRC = 'images/enemy.png'
const ENEMY_WIDTH = 60
const ENEMY_HEIGHT = 60

const __ = {
  speed: Symbol('speed')
}

const databus = new DataBus()

function rnd(start, end) {
  return Math.floor(Math.random() * (end - start) + start)
}

export default class Enemy extends Animation {
  constructor() {
    super(ENEMY_IMG_SRC, ENEMY_WIDTH, ENEMY_HEIGHT)

    this.initExplosionAnimation()
  }

  init(speed) {
    this.x = rnd(0, window.innerWidth - ENEMY_WIDTH)
    this.y = -this.height

    this[__.speed] = speed

    this.visible = true
  }

  // 预定义爆炸的帧动画
  initExplosionAnimation() {
    const frames = []

    const EXPLO_IMG_PREFIX = 'images/explosion'
    const EXPLO_FRAME_COUNT = 19

    for (let i = 0; i < EXPLO_FRAME_COUNT; i++) {
      frames.push(`${EXPLO_IMG_PREFIX + (i + 1)}.png`)
    }

    this.initFrames(frames)
  }

  // 每一帧更新子弹位置
  update() {
    this.y += this[__.speed]

    // 对象回收
    if (this.y > window.innerHeight + this.height) databus.removeEnemey(this)
  }
}

2.5 粽子子弹类实现

import Sprite from '../base/sprite'
import DataBus from '../databus'

const BULLET_IMG_SRC = 'images/bullet.png'
const BULLET_WIDTH = 16
const BULLET_HEIGHT = 30

const __ = {
  speed: Symbol('speed')
}

const databus = new DataBus()

export default class Bullet extends Sprite {
  constructor() {
    super(BULLET_IMG_SRC, BULLET_WIDTH, BULLET_HEIGHT)
  }

  init(x, y, speed) {
    this.x = x
    this.y = y

    this[__.speed] = speed

    this.visible = true
  }

  // 每一帧更新子弹位置
  update() {
    this.y -= this[__.speed]

    // 超出屏幕外回收自身
    if (this.y < -this.height) databus.removeBullets(this)
  }
}

2.6 玩家类（龙舟）

import Sprite from '../base/sprite'
import Bullet from './bullet'
import DataBus from '../databus'

const screenWidth = window.innerWidth
const screenHeight = window.innerHeight

// 玩家相关常量设置
const PLAYER_IMG_SRC = 'images/hero.png'
const PLAYER_WIDTH = 80
const PLAYER_HEIGHT = 80

const databus = new DataBus()

export default class Player extends Sprite {
  constructor() {
    super(PLAYER_IMG_SRC, PLAYER_WIDTH, PLAYER_HEIGHT)

    // 玩家默认处于屏幕底部居中位置
    this.x = screenWidth / 2 - this.width / 2
    this.y = screenHeight - this.height - 30

    // 用于在手指移动的时候标识手指是否已经在龙舟上了
    this.touched = false

    this.bullets = []

    // 初始化事件监听
    this.initEvent()
  }

  /**
   * 当手指触摸屏幕的时候
   * 判断手指是否在龙舟上
   * @param {Number} x: 手指的X轴坐标
   * @param {Number} y: 手指的Y轴坐标
   * @return {Boolean}: 用于标识手指是否在龙舟上的布尔值
   */
  checkIsFingerOnAir(x, y) {
    const deviation = 30

    return !!(x >= this.x - deviation
              && y >= this.y - deviation
              && x <= this.x + this.width + deviation
              && y <= this.y + this.height + deviation)
  }

  /**
   * 根据手指的位置设置龙舟的位置
   * 保证手指处于龙舟中间
   * 同时限定龙舟的活动范围限制在屏幕中
   */
  setAirPosAcrossFingerPosZ(x, y) {
    let disX = x - this.width / 2
    let disY = y - this.height / 2

    if (disX < 0) disX = 0

    else if (disX > screenWidth - this.width) disX = screenWidth - this.width

    if (disY <= 0) disY = 0

    else if (disY > screenHeight - this.height) disY = screenHeight - this.height

    this.x = disX
    this.y = disY
  }

  /**
   * 玩家响应手指的触摸事件
   * 改变龙舟的位置
   */
  initEvent() {
    canvas.addEventListener('touchstart', ((e) => {
      e.preventDefault()

      const x = e.touches[0].clientX
      const y = e.touches[0].clientY

      //
      if (this.checkIsFingerOnAir(x, y)) {
        this.touched = true

        this.setAirPosAcrossFingerPosZ(x, y)
      }
    }))

    canvas.addEventListener('touchmove', ((e) => {
      e.preventDefault()

      const x = e.touches[0].clientX
      const y = e.touches[0].clientY

      if (this.touched) this.setAirPosAcrossFingerPosZ(x, y)
    }))

    canvas.addEventListener('touchend', ((e) => {
      e.preventDefault()

      this.touched = false
    }))
  }

  /**
   * 玩家射击操作
   * 射击时机由外部决定
   */
  shoot() {
    const bullet = databus.pool.getItemByClass('bullet', Bullet)

    bullet.init(
      this.x + this.width / 2 - bullet.width / 2,
      this.y - 10,
      10
    )

    databus.bullets.push(bullet)
  }
}

2.7 背景类（河面）

import Sprite from '../base/sprite'

const screenWidth = window.innerWidth
const screenHeight = window.innerHeight

const BG_IMG_SRC = 'images/bg.jpg'
const BG_WIDTH = 512
const BG_HEIGHT = 512

/**
 * 游戏背景类
 * 提供update和render函数实现无限滚动的背景功能
 */
export default class BackGround extends Sprite {
  constructor(ctx) {
    super(BG_IMG_SRC, BG_WIDTH, BG_HEIGHT)

    this.top = 0

    this.render(ctx)
  }

  update() {
    this.top += 2

    if (this.top >= screenHeight) this.top = 0
  }

  /**
   * 背景图重绘函数
   * 绘制两张图片，两张图片大小和屏幕一致
   * 第一张漏出高度为top部分，其余的隐藏在屏幕上面
   * 第二张补全除了top高度之外的部分，其余的隐藏在屏幕下面
   */
  render(ctx) {
    ctx.drawImage(
      this.img,
      0,
      0,
      this.width,
      this.height,
      0,
      -screenHeight + this.top,
      screenWidth,
      screenHeight
    )

    ctx.drawImage(
      this.img,
      0,
      0,
      this.width,
      this.height,
      0,
      this.top,
      screenWidth,
      screenHeight
    )
  }
}

2.8 展示分数和结算界面实现

const screenWidth = window.innerWidth
const screenHeight = window.innerHeight

const atlas = new Image()
atlas.src = 'images/Common.png'

export default class GameInfo {
  renderGameScore(ctx, score) {
    ctx.fillStyle = '#ffffff'
    ctx.font = '20px Arial'

    ctx.fillText(
      score,
      10,
      30
    )
  }

  renderGameOver(ctx, score) {
    ctx.drawImage(atlas, 0, 0, 119, 108, screenWidth / 2 - 150, screenHeight / 2 - 100, 300, 300)

    ctx.fillStyle = '#ffffff'
    ctx.font = '20px Arial'

    ctx.fillText(
      '游戏结束',
      screenWidth / 2 - 40,
      screenHeight / 2 - 100 + 50
    )

    ctx.fillText(
      `得分: ${score}`,
      screenWidth / 2 - 40,
      screenHeight / 2 - 100 + 130
    )

    ctx.drawImage(
      atlas,
      120, 6, 39, 24,
      screenWidth / 2 - 60,
      screenHeight / 2 - 100 + 180,
      120, 40
    )

    ctx.fillText(
      '重新开始',
      screenWidth / 2 - 40,
      screenHeight / 2 - 100 + 205
    )

    /**
     * 重新开始按钮区域
     * 方便简易判断按钮点击
     */
    this.btnArea = {
      startX: screenWidth / 2 - 40,
      startY: screenHeight / 2 - 100 + 180,
      endX: screenWidth / 2 + 50,
      endY: screenHeight / 2 - 100 + 255
    }
  }
}

2.9 全局音效管理器实现

let instance

/**
 * 统一的音效管理器
 */
export default class Music {
  constructor() {
    if (instance) return instance

    instance = this

    this.bgmAudio = new Audio()
    this.bgmAudio.loop = true
    this.bgmAudio.src = 'audio/bgm.mp3'

    this.shootAudio = new Audio()
    this.shootAudio.src = 'audio/bullet.mp3'

    this.boomAudio = new Audio()
    this.boomAudio.src = 'audio/boom.mp3'

    this.playBgm()
  }

  playBgm() {
    this.bgmAudio.play()
  }

  playShoot() {
    this.shootAudio.currentTime = 0
    this.shootAudio.play()
  }

  playExplosion() {
    this.boomAudio.currentTime = 0
    this.boomAudio.play()
  }
}

2.10 管控游戏状态实现

import Pool from './base/pool'

let instance

/**
 * 全局状态管理器
 */
export default class DataBus {
  constructor() {
    if (instance) return instance

    instance = this

    this.pool = new Pool()

    this.reset()
  }

  reset() {
    this.frame = 0
    this.score = 0
    this.bullets = []
    this.enemys = []
    this.animations = []
    this.gameOver = false
  }

  /**
   * 回收敌人，进入对象池
   * 此后不进入帧循环
   */
  removeEnemey(enemy) {
    const temp = this.enemys.shift()

    temp.visible = false

    this.pool.recover('enemy', enemy)
  }

  /**
   * 回收子弹，进入对象池
   * 此后不进入帧循环
   */
  removeBullets(bullet) {
    const temp = this.bullets.shift()

    temp.visible = false

    this.pool.recover('bullet', bullet)
  }
}

2.11 游戏入口主函数实现

import Player from './player/index'
import Enemy from './npc/enemy'
import BackGround from './runtime/background'
import GameInfo from './runtime/gameinfo'
import Music from './runtime/music'
import DataBus from './databus'

const ctx = canvas.getContext('2d')
const databus = new DataBus()

/**
 * 游戏主函数
 */
export default class Main {
  constructor() {
    // 维护当前requestAnimationFrame的id
    this.aniId = 0

    this.restart()
  }

  restart() {
    databus.reset()

    canvas.removeEventListener(
      'touchstart',
      this.touchHandler
    )

    this.bg = new BackGround(ctx)
    this.player = new Player(ctx)
    this.gameinfo = new GameInfo()
    this.music = new Music()

    this.bindLoop = this.loop.bind(this)
    this.hasEventBind = false

    // 清除上一局的动画
    window.cancelAnimationFrame(this.aniId)

    this.aniId = window.requestAnimationFrame(
      this.bindLoop,
      canvas
    )
  }

  /**
   * 随着帧数变化的敌机生成逻辑
   * 帧数取模定义成生成的频率
   */
  enemyGenerate() {
    if (databus.frame % 30 === 0) {
      const enemy = databus.pool.getItemByClass('enemy', Enemy)
      enemy.init(6)
      databus.enemys.push(enemy)
    }
  }

  // 全局碰撞检测
  collisionDetection() {
    const that = this

    databus.bullets.forEach((bullet) => {
      for (let i = 0, il = databus.enemys.length; i < il; i++) {
        const enemy = databus.enemys[i]

        if (!enemy.isPlaying && enemy.isCollideWith(bullet)) {
          enemy.playAnimation()
          that.music.playExplosion()

          bullet.visible = false
          databus.score += 1

          break
        }
      }
    })

    for (let i = 0, il = databus.enemys.length; i < il; i++) {
      const enemy = databus.enemys[i]

      if (this.player.isCollideWith(enemy)) {
        databus.gameOver = true

        break
      }
    }
  }

  // 游戏结束后的触摸事件处理逻辑
  touchEventHandler(e) {
    e.preventDefault()

    const x = e.touches[0].clientX
    const y = e.touches[0].clientY

    const area = this.gameinfo.btnArea

    if (x >= area.startX
        && x <= area.endX
        && y >= area.startY
        && y <= area.endY) this.restart()
  }

  /**
   * canvas重绘函数
   * 每一帧重新绘制所有的需要展示的元素
   */
  render() {
    ctx.clearRect(0, 0, canvas.width, canvas.height)

    this.bg.render(ctx)

    databus.bullets
      .concat(databus.enemys)
      .forEach((item) => {
        item.drawToCanvas(ctx)
      })

    this.player.drawToCanvas(ctx)

    databus.animations.forEach((ani) => {
      if (ani.isPlaying) {
        ani.aniRender(ctx)
      }
    })

    this.gameinfo.renderGameScore(ctx, databus.score)

    // 游戏结束停止帧循环
    if (databus.gameOver) {
      this.gameinfo.renderGameOver(ctx, databus.score)

      if (!this.hasEventBind) {
        this.hasEventBind = true
        this.touchHandler = this.touchEventHandler.bind(this)
        canvas.addEventListener('touchstart', this.touchHandler)
      }
    }
  }

  // 游戏逻辑更新主函数
  update() {
    if (databus.gameOver) return

    this.bg.update()

    databus.bullets
      .concat(databus.enemys)
      .forEach((item) => {
        item.update()
      })

    this.enemyGenerate()

    this.collisionDetection()

    if (databus.frame % 20 === 0) {
      this.player.shoot()
      this.music.playShoot()
    }
  }

  // 实现游戏帧循环
  loop() {
    databus.frame++

    this.update()
    this.render()

    this.aniId = window.requestAnimationFrame(
      this.bindLoop,
      canvas
    )
  }
}

3 结束语

上述主要介绍了小游戏关键的实现点，在该游戏的场景下，如果有兴趣的同学可以将粽子类在多添加几个，让粽子的种类多起来，这样可玩性很高！我主要是起一个抛砖引玉的作用，再次祝福大家端午节万事顺遂，多多吃粽子，吃好喝好！
下附小游戏源码下载地址：https://github.com/41809310102/mygames

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